[Treeve]

In the FWIW category on this, the bending moment is created in relation to the the two areas that you suggest with the shock acting as a simple support for the wheel to impose the moment around. The weld failed in the heat affected zone and hence is exactly where a failure would be expected if it were not a cracked weld in and of itself. So the failure has a lot to do with design. And the American system is a lot more free than the Australian system.